U.S. patent application number 15/811157 was filed with the patent office on 2018-03-08 for observation system and observation method.
This patent application is currently assigned to FUJITSU LIMITED. The applicant listed for this patent is Fujitsu Limited. Invention is credited to Koji KURIHARA, Takahisa SUZUKI, Koichiro YAMASHITA.
Application Number | 20180067218 15/811157 |
Document ID | / |
Family ID | 57441921 |
Filed Date | 2018-03-08 |
United States Patent
Application |
20180067218 |
Kind Code |
A1 |
KURIHARA; Koji ; et
al. |
March 8, 2018 |
OBSERVATION SYSTEM AND OBSERVATION METHOD
Abstract
An observation system includes a server and a plurality of
nodes. The server transmits data to the plurality of nodes and
receives response data from the plurality of nodes. The server
determines an incoming data-unit count and calculates a ratio of
nodes that perform data transmission so that the server receives at
least as many data units as a requested data-unit count to the
plurality of nodes. The server sends information about the ratio to
the plurality of nodes. Each of nodes transmits data to the server
in accordance with the information about the ratio.
Inventors: |
KURIHARA; Koji; (Kawasaki,
JP) ; YAMASHITA; Koichiro; (Hachioji, JP) ;
SUZUKI; Takahisa; (Yokohama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fujitsu Limited |
Kawasaki-shi |
|
JP |
|
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
57441921 |
Appl. No.: |
15/811157 |
Filed: |
November 13, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2015/066407 |
Jun 5, 2015 |
|
|
|
15811157 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04Q 2209/886 20130101;
G01V 1/18 20130101; H04Q 2209/40 20130101; G08C 25/00 20130101;
H04Q 9/00 20130101; H04L 67/12 20130101; G01V 1/22 20130101; H04Q
2209/25 20130101; H04W 4/38 20180201; G01V 1/223 20130101; G01W
1/02 20130101; G01V 1/04 20130101 |
International
Class: |
G01V 1/22 20060101
G01V001/22; G08C 25/00 20060101 G08C025/00; G01V 1/04 20060101
G01V001/04 |
Claims
1. An observation system comprising: a plurality of nodes; and a
server comprising: a processor that executes a process comprising:
transmitting data to the plurality of nodes; receiving response
data from the plurality of nodes; first determining an incoming
data-unit count, the incoming data-unit count being the number of
response data units incoming from the plurality of nodes to the
server; calculating a ratio of nodes that perform data transmission
so that the server receives at least as many data units as a
requested data-unit count to the plurality of nodes based on a data
missing ratio and the requested data-unit count, the data missing
ratio being obtained from the incoming data-unit count and a total
node count, the total node count being the number of the nodes
included in the system; and sending information about the ratio
calculated by the calculating to the plurality of nodes, wherein,
each of nodes transmits data to the server in accordance with the
information about the ratio.
2. The observation system according to claim 1, wherein the process
further comprises second determining whether the incoming data-unit
count is smaller than the requested data-unit count and the process
executes the first determining, the calculating and sending again
when the incoming data-unit count is smaller than the requested
data-unit count.
3. The observation system according to claim 1, wherein the
calculating calculates a first value obtained by subtracting the
missing ratio from one, a product by multiplying the first value by
the total node count and second value by dividing the requested
data-unit count by the product, wherein the second value is equal
to the ratio of nodes.
4. The observation system according to claim 1, wherein the each of
nodes generates a random variable, compares the generated random
variable against the information about the ratio, and transmits a
data unit in accordance with a result of the comparison.
5. An observation method comprising: transmitting at which a server
transmits data to a plurality of nodes; receiving at which the
sever receives response data from the plurality of nodes;
determining at which the server determines an incoming data-unit
count, the incoming data-unit count being the number of response
data units incoming from the plurality of nodes to the server;
calculating at which the server calculates a ratio of nodes that
perform data transmission so that the server receives at least as
many data units as a requested data-unit count to the plurality of
nodes based on a data missing ratio and the requested data-unit
count, the data missing ratio being obtained from the incoming
data-unit count and a total node count, the total node count being
the number of the nodes included in the system; sending at which
the server sends information about the ratio calculated by the
calculating to the plurality of nodes; and transmitting at which
each of nodes transmits data to the server in accordance with the
information about the ratio.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of International
Application No. PCT/JP2015/066407, filed on Jun. 5, 2015, the
entire contents of which are incorporated herein by reference.
FIELD
[0002] The embodiment discussed herein is related to observation
systems and the like.
BACKGROUND
[0003] A monitoring technique, in which an observation apparatus
gathers various types of environmental information using a wireless
sensor network where a plurality of sensor nodes that perform
wireless communication is arranged, has been proposed. Examples of
the environmental information include information about
temperature, humidity, soil water content, and acceleration.
Hereinafter, a wireless sensor network is referred to as "WSN".
[0004] Each sensor node of the WSN is powered by a solar battery or
the like and performs measurement to obtain environmental
information over a long period. This limits the amount of electric
power the sensor node can use in wireless communication. For this
reason, each sensor node transmits environmental information to the
observation apparatus, which is distant from the sensor node, by
multi-hop communication that relays the environmental information
to an adjacent another sensor node rather than transmitting the
environmental information directly to the observation
apparatus.
[0005] Each sensor node, for which sensing interval is set in
advance, of the WSN performs measurement to obtain an environmental
information unit each time the sensing interval elapses and
transmits the measured environmental information unit to a parent
server.
[0006] Patent Document 1: Japanese Laid-open Patent Publication No.
2003-115092
[0007] Patent Document 2: Japanese Laid-open Patent Publication No.
2011-013765
[0008] Patent Document 3: Japanese Laid-open Patent Publication No.
2012-080622
[0009] However, the above-described conventional technique is
disadvantageous in that shortage in the number of environmental
information units transmitted from the sensor nodes to the
observation apparatus can occur.
[0010] For example, the larger the number of sensor nodes included
in a WSN, the more congestion between nodes is likely to occur,
which can lead to a failure of environmental information units
obtained by sensor nodes through measurement to reach the parent
server. When the observation apparatus fails to obtain a minimum
number of environmental information units, it is difficult for the
observation apparatus to conduct accurate monitoring.
SUMMARY
[0011] According to an aspect of an embodiment, an observation
system includes a plurality of nodes; and a server including: a
processor that executes a process including: transmitting data to
the plurality of nodes; receiving, response data from the plurality
of nodes; first determining an incoming data-unit count, the
incoming data-unit count being the number of response data units
incoming from the plurality of nodes to the server; calculating a
ratio of nodes that perform data transmission so that the server
receives at least as many data units as a requested data-unit count
to the plurality of nodes based on a data missing ratio and the
requested data-unit count, the data missing ratio being obtained
from the incoming data-unit count and a total node count, the total
node count being the number of the nodes included in the system;
and sending information about the ratio calculated by the
calculating to the plurality of nodes, wherein, each of nodes
transmits data to the server in accordance with the information
about the ratio.
[0012] The object and advantages of the invention will be realized
and attained by means of the elements and combinations particularly
pointed out in the claims.
[0013] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a diagram illustrating an example of an
observation system according to an embodiment;
[0015] FIG. 2 is a sequence diagram of the observation system;
[0016] FIG. 3 is a functional block diagram illustrating a
configuration of an observation apparatus;
[0017] FIG. 4 is a functional block diagram illustrating a
configuration of a node;
[0018] FIG. 5 is a flowchart illustrating a procedure for
processing of the observation apparatus;
[0019] FIG. 6 is a flowchart illustrating a processing procedure
for profiling;
[0020] FIG. 7 is a flowchart illustrating a processing procedure
for monitoring;
[0021] FIG. 8 is a flowchart illustrating a procedure for
processing of a node;
[0022] FIG. 9 is a flowchart illustrating a processing procedure
for cycle measurement;
[0023] FIG. 10 is a diagram illustrating a hardware configuration
of a node; and
[0024] FIG. 11 is a diagram illustrating an example of a computer
that executes an observation program.
DESCRIPTION OF EMBODIMENT(S)
[0025] Preferred embodiments of the present invention will be
explained with reference to accompanying drawings. The embodiment
is not intended to limit the disclosure in any way.
[0026] FIG. 1 is a diagram illustrating an example of an
observation system according to the embodiment. As illustrated in
FIG. 1, the observation system includes an observation apparatus
100 and nodes 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i, and 10j.
The observation apparatus 100 is an example of "server". Although
an example where the observation system includes the nodes 10a to
10j is illustrated, the observation system may include one or more
other nodes. The nodes 10a to 10j may be collectively denoted as
"the nodes 10" as appropriate.
[0027] Each of the nodes 10 is charged with an energy harvester or
the like and executes various processing triggered by, for
instance, wireless reception or sensor response. The node 10
wirelessly transmits an environmental information unit obtained by
measurement using a sensor and other information. When a battery is
depleted, the node 10 is recharged to repeatedly execute processing
described above. Examples of the environmental information unit
include information about temperature, humidity, soil water
content, and acceleration.
[0028] The node 10 transmits the environmental information unit and
other information to the observation apparatus 100 via multi-hop
communication. This limits the amount of electric power the node 10
can use in wireless transmission and, accordingly, makes a radio
range of the node 10 short. For this reason, when distant from the
observation apparatus 100, the node 10 is unable to perform direct
wireless communication with the observation apparatus 100. In such
a case, the node 10 transmits data to the observation apparatus 100
via multi-hop communication, in which the data is relayed via
another one or more of the nodes 10.
[0029] For instance, data, which is destined for the observation
apparatus 100, transmitted from the node 10j is relayed via the
nodes 10h and 10a to reach the observation apparatus 100. Data,
which is destined for the node 10j, transmitted from the
observation apparatus 100 is relayed via the nodes 10a and 10h to
reach the node 10j.
[0030] In case of occurrence of data missing due to, for instance,
congestion, the node 10 performs retransmission control to transmit
the data again.
[0031] The observation apparatus 100 performs profiling and
monitoring. The profiling, which is to be performed by the
observation apparatus 100, is described first. The observation
apparatus 100 transmits a "data gathering instruction" to all the
nodes 10 included in the observation system. Upon receiving the
data gathering instruction, each of the nodes 10 transmits a
response data unit destined for the observation apparatus 100.
[0032] The observation apparatus 100 receives response data units
from the nodes 10 and determines the number of the response data
units. Hereinafter, the number of the response data units is
denoted as "arrived data-unit count" as appropriate. The
observation apparatus 100 calculates a missing ratio from a total
node count, which is the number of all the nodes 10 included in the
observation system, and the arrived data-unit count. The
observation apparatus 100 also calculates a measurement execution
probability from the total node count, the missing ratio, and a
requested data-unit count. The observation apparatus 100 informs
all the nodes 10 included in the observation system of the
measurement execution probability and proceeds to the monitoring,
which is described below.
[0033] The requested data-unit count is a value set by an
administrator in advance. When the requested data-unit count is
specified, the observation apparatus 100 performs the monitoring on
condition that the number of data units received from the nodes 10
be larger than or equal to the requested data-unit count. The
measurement execution probability is a ratio of a minimum number of
the nodes 10 that perform data transmission so that the observation
apparatus 100 receives at least as many data units as the requested
data-unit count to the number of all the nodes 10.
[0034] Next, the monitoring, which is to be performed by the
observation apparatus 100, is described. The observation apparatus
100 transmits a "cyclical data gathering instruction" to all the
nodes 10 included in the observation system. Upon receiving the
cyclical data gathering instruction, each of the nodes 10 starts a
cyclical operation. During the operation, the node 10 generates a
random variable and, when the random variable is smaller than or
equal to the measurement execution probability, the node 10
transmits an environmental information unit to the observation
apparatus 100. On the other hand, when the random variable is
larger than the measurement execution probability, the node 10
suspends transmission of the environmental information unit until
another random variable is generated in the next cycle.
[0035] Upon receiving environmental information units of one cycle,
the observation apparatus 100 compares the number of the
environmental information units of one cycle against the requested
data-unit count. When the number of environmental information units
is larger than or equal to the requested data-unit count, the
observation apparatus 100 continues processing of receiving
environmental information units transmitted every cycle. On the
other hand, when the number of environmental information units is
smaller than the requested data-unit count, the observation
apparatus 100 proceeds to the profiling.
[0036] FIG. 2 is a sequence diagram of the observation system. The
nodes 10a and 10j are illustrated in FIG. 2, but illustration of
the other nodes 10 is omitted. A procedure for the profiling is
described below. The observation apparatus 100 transmits the data
gathering instruction to the nodes 10 (S10). Upon receiving the
data gathering instruction, the node 10a transmits a response data
unit to the observation apparatus 100 (S11). Upon receiving the
data gathering instruction, the node 10j transmits a response data
unit to the observation apparatus 100 (S12).
[0037] Upon receiving the response data units from the nodes 10,
the observation apparatus 100 calculates a measurement execution
probability (S13). The observation apparatus 100 informs the nodes
10a and 10j of the measurement execution probability (S14).
[0038] A procedure for the monitoring is described below. The
observation apparatus 100 transmits a cyclical data gathering
instruction to the nodes 10 (S20). Upon receiving the cyclical data
gathering instruction, the nodes 10a and 10j perform an operation
of a cycle T1 and an operation of a cycle T2.
[0039] The cycle T1 is described below. The node 10a makes
execution determination or, specifically, generates a random
variable and compares the random variable against the measurement
execution probability (S21). When the random variable is smaller
than or equal to the measurement execution probability, the node
10a performs sensing to acquire an environmental information unit
(S22). The node 10a transmits the environmental information unit to
the observation apparatus 100 (S23).
[0040] The node 10j makes execution determination or, specifically,
generates a random variable and compares the random variable
against the measurement execution probability (S24). When the
random variable is smaller than or equal to the measurement
execution probability, the node 10j performs sensing to acquire an
environmental information unit (S25). The node 10j transmits the
environmental information unit to the observation apparatus 100
(S26).
[0041] The cycle T2 is described below. The node 10a makes
execution determination or, specifically, generates a random
variable and compares the random variable against the measurement
execution probability (S27). When the random variable is larger
than the measurement execution probability, the node 10a is on
standby until the next cycle.
[0042] The node 10j makes execution determination or, specifically,
generates a random variable and compares the random variable
against the measurement execution probability (S28). When the
random variable is smaller than or equal to the measurement
execution probability, the node 10j performs sensing to acquire an
environmental information unit (S29). The node 10j transmits the
environmental information unit to the observation apparatus 100
(S30).
[0043] As described above, in the observation system according to
the embodiment, the observation apparatus 100 calculates a
measurement execution probability using a missing ratio of data
units transmitted from all the nodes 10 and informs all the nodes
10 of the measurement execution probability. Each of the nodes 10
controls transmission of an environmental information unit in
accordance with the informed measurement execution probability.
Hence, occurrence of a situation where all the nodes 10
simultaneously transmit environmental information units can be at
least reduced. This allows obtaining as many environmental
information units as the requested data-unit count or more while
preventing congestion. Furthermore, because congestion is less
likely to occur, data missing can be prevented, frequency of when
the node 10 retransmits an environmental information unit is
reduced, and reduction in power consumption can be achieved.
[0044] An example of a configuration of the observation apparatus
100 is described below. FIG. 3 is a functional block diagram
illustrating the configuration of the observation apparatus. As
illustrated in FIG. 3, the observation apparatus 100 includes a
communication unit 110, an input unit 120, a display unit 130, a
storage unit 140, and a control unit 150.
[0045] The communication unit 110 is a communication device that
performs data communication with the nodes 10 via wireless
communication. The control unit 150, which is described below,
exchanges data with the nodes 10 via the communication unit
110.
[0046] The input unit 120 is an input device that inputs a variety
of information to the observation apparatus 100. The input device
corresponds to an input device, which may be, for instance, a
keyboard, a mouse, and/or a touch panel.
[0047] The display unit 130 is a display device that displays
information output from the control unit 150. The display unit 130
corresponds to, for instance, a display or a touch panel.
[0048] The storage unit 140 includes requested-data-unit-count
information 141, total-node-count information 142, and
receipt-count information 143. The storage unit 140 corresponds to,
for instance, a storage device, such as a semiconductor memory
device, examples of which include a random access memory (RAM), a
read only memory (ROM), and a flash memory.
[0049] The requested-data-unit-count information 141 is information
about the requested data-unit count that is set by the
administrator or the like. The administrator enters the
requested-data-unit-count information 141 to the observation
apparatus 100 by operating the input unit 120.
[0050] The total-node-count information 142 is information about
the total node count, which is the total number of nodes included
in the observation system. For instance, the administrator that has
acquired the total node count in advance may enter the
total-node-count information 142 to the observation apparatus 100
by operating the input unit 120.
[0051] The receipt-count information 143 is information indicating
a receipt count, which is the number of environmental information
units received in one cycle. The receipt-count information 143 may
hold cycle-by-cycle receipt counts of environmental information
units.
[0052] The control unit 150 includes a determining unit 151, a
calculation unit 152, a notification unit 153, and a judging unit
154. The control unit 150 may correspond to, for instance, an
integrated device, such as an application specific integrated
circuit (ASIC) or a field programmable gate array (FPGA). The
control unit 150 may correspond to, for instance, an electronic
circuit, such as a central processing unit (CPU) or a micro
processing unit (MPU).
[0053] The determining unit 151 is a processing unit that
determines an arrived data-unit count by transmitting the data
gathering instruction to the nodes 10 of the observation system and
aggregating the number of response data units transmitted from the
nodes 10. The determining unit 151 outputs information about the
arrived data-unit count to the calculation unit 152. The
determining unit 151 determines, as the arrived data-unit count,
for instance, the number of response data units received from the
nodes 10 in a fixed period of time, which corresponds to one cycle,
from when the data gathering instruction is transmitted.
[0054] The calculation unit 152 is a processing unit that
calculates a missing ratio and a measurement execution probability.
The calculation unit 152 outputs information about the measurement
execution probability to the notification unit 153. Processing,
through which the calculation unit 152 calculates a missing ratio,
is described below. The calculation unit 152 calculates a missing
ratio using Equation (1). In Equation (1), n, an arrived data-unit
count, corresponds to the arrived data-unit count fed to the
calculation unit 152 from the determining unit 151. N, a total node
count, corresponds to the total number of nodes contained in the
total-node-count information 142.
missing ratio Z=n/N (1)
[0055] Processing, through which the calculation unit 152
calculates a measurement execution probability, is described below.
The calculation unit 152 calculates a measurement execution
probability using Equation (2). In Equation (2), Y, a requested
data-unit count, corresponds to the requested data-unit count
contained in the requested-data-unit-count information 141. N, the
total node count, corresponds to the total node count contained in
the total-node-count information 142. Z, the missing ratio, is the
missing ratio Z calculated using Equation (1). .alpha. is a margin
that is set by the administrator as appropriate.
measurement execution probability P=Y/N.times.(1-Z)+.alpha. (2)
[0056] In Equation (2), the measurement execution probability P is
a value corresponding to a ratio of a minimum number of nodes that
perform data transmission so that at least as many data units as
the requested data-unit count are gathered to the total node
count.
[0057] The notification unit 153 is a processing unit that
transmits information about the measurement execution probability
to all the nodes 10 of the observation system. Upon completing
transmission of the information about the measurement execution
probability, the notification unit 153 outputs information
indicating completion of the profiling to the judging unit 154.
[0058] Processing described above performed by the determining unit
151, the calculation unit 152, and the notification unit 153
correspond to the profiling.
[0059] Upon receiving the information indicating completion of the
profiling, the judging unit 154 starts the monitoring by
transmitting the cyclical data gathering instruction to all the
nodes 10 of the observation system. Each time one cycle elapses,
the judging unit 154 counts a receipt count of one cycle, which is
the number of environmental information units received in the one
cycle, and stores the receipt count in the receipt-count
information 143. The judging unit 154 compares the receipt count of
one cycle against the requested data-unit count and, when the
number of the data units of one cycle is larger than or equal to
the requested data-unit count, continues the monitoring.
[0060] On the other hand, the judging unit 154 compares the receipt
count of one cycle against the requested data-unit count and, when
the number of the data units of one cycle is smaller than the
requested data-unit count, the judging unit 154 issues a profiling
request to the determining unit 151, the calculation unit 152, and
the notification unit 153 again.
[0061] Upon receiving the profiling request, the determining unit
151, the calculation unit 152, and the notification unit 153
perform the profiling again.
[0062] An example of a configuration of the node 10 is described
below. FIG. 4 is a functional block diagram illustrating the
configuration of the node. As illustrated in FIG. 4, the node 10
includes a communication unit 11, a sensor 12, a battery 13, a
storage unit 14, and a control unit 15.
[0063] The communication unit 11 is a processing unit that performs
data communication with another node 10 and the observation
apparatus 100 via wireless communication. The control unit 15,
which is described below, exchanges data with the other node 10 and
the observation apparatus 100 via the communication unit 11.
[0064] The sensor 12 is a sensor that performs measurement to
obtain various types of environmental information. For instance,
the sensor 12 measures, as environmental information, temperature,
humidity, soil water content, and acceleration.
[0065] The battery 13 is a battery to be charged using an energy
harvester, such as a solar panel.
[0066] The storage unit 14 holds environmental information 14a,
measurement-execution-probability information 14b, and a route
table 14c. The storage unit 14 corresponds to, for instance, a
storage device, such as a semiconductor memory device, examples of
which include a RAM, a ROM, and a flash memory.
[0067] The environmental information 14a is environmental
information obtained through measurement using the sensor 12. The
measurement-execution-probability information 14b is information
about the measurement execution probability informed by the
observation apparatus 100. The route table 14c contains information
about a route for transmitting data to a destination. For instance,
the route table 14c associates a destination with an adjacent node
on a way to the destination.
[0068] The control unit 15 includes a measurement unit 15a and a
transceiving unit 15b. The control unit 15 may correspond to, for
instance, an integrated device, such as an ASIC or an FPGA. The
control unit 15 may correspond to, for instance, an electronic
circuit, such as a CPU or an MPU. The control unit 15 performs an
intermittent operation using a not-illustrated timer or the like in
regular cycles that are set in advance. The control unit 15 may
iterate a sequence, in which the control unit 15 starts the
operation when a change in environmental information is detected by
the sensor 12 and enters a sleep mode when a predetermined period
time has elapsed since the start of the operation.
[0069] The measurement unit 15a is a processing unit that acquires
the environmental information 14a from the sensor 12 and stores the
acquired environmental information 14a in the storage unit 14.
[0070] Upon receiving the data gathering instruction from the
observation apparatus 100, the transceiving unit 15b transmits a
response data unit to the observation apparatus 100. Upon receiving
the measurement-execution-probability information 14b from the
observation apparatus 100, the transceiving unit 15b stores the
measurement-execution-probability information 14b in the storage
unit 14.
[0071] The transceiving unit 15b generates a random variable, which
ranges between 0 and 1, using a random function and compares the
random variable against the measurement execution probability of
the measurement-execution-probability information 14b. When the
random variable is smaller than or equal to the measurement
execution probability, the transceiving unit 15b transmits the
environmental information 14a to the observation apparatus 100. On
the other hand, when the random variable is larger than the
measurement execution probability, the transceiving unit 15b
suspends transmission of the environmental information 14a to the
observation apparatus 100.
[0072] A procedure for processing of the observation apparatus 100
according to the embodiment is described below. FIG. 5 is a
flowchart illustrating the procedure for processing of the
observation apparatus. As illustrated in FIG. 5, the observation
apparatus 100 performs the profiling (S101). The observation
apparatus 100 performs the monitoring (S102). When processing is
not to be ended (No at S103), the observation apparatus 100 moves
to S101. When processing is to be ended (Yes at S103), the
observation apparatus 100 completes processing.
[0073] A processing procedure for the profiling illustrated in S101
of FIG. 5 is described below. FIG. 6 is a flowchart illustrating
the processing procedure for the profiling. As illustrated in FIG.
6, the determining unit 151 of the observation apparatus 100
transmits the data gathering instruction to all the nodes 10 (S150)
and receives response data units (S151).
[0074] The determining unit 151 determines whether the fixed period
of time has elapsed (S152). When the fixed period of time has not
elapsed (No at S152), the determining unit 151 moves to S151. On
the other hand, when the fixed period of time has elapsed (Yes at
S152), the calculation unit 152 of the observation apparatus 100
calculates a measurement execution probability (S153). The
notification unit 153 of the observation apparatus 100 transmits
the measurement execution probability to all the nodes 10
(S154).
[0075] A processing procedure for the monitoring illustrated in
S102 of FIG. 5 is described below. FIG. 7 is a flowchart
illustrating the processing procedure for the monitoring. As
illustrated in FIG. 7, the judging unit 154 of the observation
apparatus 100 transmits the cyclical data gathering instruction to
all the nodes 10 (S161).
[0076] The judging unit 154 receives environmental information
units (S162). The judging unit 154 determines whether environmental
information units of one cycle have been received (S163). When
environmental information units of one cycle have not been received
(No at S163), the judging unit 154 moves to S162. When
environmental information units of one cycle have been received
(Yes at S163), the judging unit 154 moves to S164.
[0077] The judging unit 154 compares a receipt count against the
requested data-unit count (S164). When the receipt count is smaller
than the requested data-unit count (Yes at S165), the judging unit
154 completes the monitoring. On the other hand, when the receipt
count is not smaller than the requested data-unit count (No at
S165), the judging unit 154 moves to S162.
[0078] A procedure for processing of the node 10 is described
below. FIG. 8 is a flowchart illustrating the procedure for
processing of the node. As illustrated in FIG. 8, the node 10
determines whether the data gathering instruction has been received
(S201). When the data gathering instruction has not been received
(No at S201), the node 10 moves to S201 again.
[0079] When the data gathering instruction has been received (Yes
at S201), the node 10 transmits a response data unit (S202). The
node 10 determines whether a measurement execution probability has
been received (S203). When a measurement execution probability has
not been received (No at S203), the node 10 moves to S203
again.
[0080] When a measurement execution probability has been received
(Yes at S203), the node 10 stores the measurement execution
probability (S204). The node 10 determines whether the cyclical
data gathering instruction has been received (S205). When the
cyclical data gathering instruction has not been received (No at
S205), the node 10 moves to S205 again.
[0081] When the cyclical data gathering instruction has been
received (Yes at S205), the node 10 performs cycle measurement
(S206). The node 10 determines whether the data gathering
instruction has been received (S207). When the data gathering
instruction has not been received (No at S207), the node 10 moves
to S209.
[0082] When the data gathering instruction has been received (Yes
at S207), the node 10 transmits a response data unit (S208) and
moves to S209.
[0083] The node 10 determines whether a measurement execution
probability has been received (S209). When a measurement execution
probability has not been received (No at S209), the node 10 moves
to S206. When a measurement execution probability has been received
(Yes at S209), the node 10 stores the measurement execution
probability (S210) and moves to S206.
[0084] A processing procedure for the cycle measurement illustrated
in S206 of FIG. 8 is described below. FIG. 9 is a flowchart
illustrating the processing procedure for the cycle measurement. As
illustrated in FIG. 9, the node 10 determines whether a one cycle
has elapsed (S250). When a one cycle has not elapsed (No at S250),
the node 10 completes the cycle measurement.
[0085] On the other hand, when a one cycle has elapsed (Yes at
S250), the node 10 generates a random variable (S251). When the
random variable is smaller than or equal to the measurement
execution probability (No at S252), the node 10 transmits an
environmental information unit (S253) and completes the cycle
measurement. When the random variable is larger than the
measurement execution probability (Yes at S252), the node 10
completes the cycle measurement.
[0086] Advantageous effects of the observation system according to
the embodiment are described below. The observation apparatus 100
calculates a measurement execution probability using a missing
ratio of response data units transmitted from all the nodes 10 and
informs all the nodes 10 of the measurement execution probability.
Each of the nodes 10 controls transmission of an environmental
information unit in accordance with the informed measurement
execution probability. Hence, occurrence of a situation where all
the nodes 10 simultaneously transmit environmental information
units to the observation apparatus 100 can be at least reduced.
This allows obtaining as many environmental information units as
the requested data-unit count or more while preventing congestion.
Furthermore, because congestion is less likely to occur, data
missing can be prevented, frequency of when the node 10 retransmits
an environmental information unit decreases, and reduction in
electric power consumed in retransmission can be achieved.
[0087] An example of a hardware configuration of the node 10 is
described below. FIG. 10 is a diagram illustrating the hardware
configuration of the node. The node 10 includes, for instance, a
sensing device 21, an energy harvester 22, a battery 23, a radio
unit 24, a power controller 25, and a processor 26.
[0088] The sensing device 21 is the sensor that performs
measurement to obtain environmental information. The energy
harvester 22 is a device that generates a minute amount of
electricity using, for instance, ambient radio frequency or
temperature. The battery 23 is a battery that accumulates the
electricity generated by the energy harvester 22. The radio 24 is a
device that performs data communication with another node. The
power controller 25 is a device that performs power management of
the node 10. The processor 26 is a device that executes processing
corresponding to the control unit 15 illustrated in FIG. 4.
[0089] An example of a computer that executes observation program
instructions (hereinafter, "program") that implement functions
similar to those of the observation apparatus 100 presented in the
above-described embodiment is described below. FIG. 11 is a diagram
describing an example of the computer that executes the observation
program.
[0090] As illustrated in FIG. 11, a computer 200 includes a CPU 201
that executes various computing processing, an input device 202
that receives data entered by a user, and a display 203. The
computer 200 further includes a reading device 204 that reads
program instructions or the like from a storage medium and an
interface device 205 that transmits and receives data to and from
another computer via a network. The computer 200 further includes a
RAM 206 that temporarily stores various types of information and a
storage device 207. The devices 201 to 207 are connected to a bus
208.
[0091] The storage device 207 holds, for instance, a determining
program 207a, a calculation program 207b, and a notification
program 207c. The CPU 201 reads out and loads the determining
program 207a, the calculation program 207b, and the notification
program 207c into the RAM 206. The determining program 207a
functions as a determining process 206a. The calculation program
207b functions as a calculation process 206b. The notification
program 207c functions as a notification process 206c.
[0092] Processing of the determining process 206a corresponds to
processing of the determining unit 151. Processing of the
calculation process 206b corresponds to processing of the
calculation unit 152. Processing of the notification process 206c
corresponds to processing of the notification unit 153.
[0093] The determining program 207a, the calculation program 207b,
and the notification program 207c are not necessarily stored in the
storage device 207 in advance. For instance, the following
configuration may alternatively be employed. The programs 207a to
207c are stored in advance in a "portable physical medium", such as
a flexible disk (FD), a compact disk read-only memory (CD-ROM), a
digital versatile disc (DVD), a magneto-optical disk, or an
integrated circuit (IC) card, to be inserted into the computer 200.
The computer 200 reads out the programs 207a to 207c from the
physical medium and executes the programs 207a to 207c.
[0094] According to the embodiment, occurrence of shortage in the
number of environmental information units transmitted from sensor
nodes to an observation apparatus can be at least reduced.
[0095] All examples and conditional language recited herein are
intended for pedagogical purposes of aiding the reader in
understanding the invention and the concepts contributed by the
inventor to further the art, and are not to be construed as
limitations to such specifically recited examples and conditions,
nor does the organization of such examples in the specification
relate to a showing of the superiority and inferiority of the
invention. Although the embodiment of the present invention has
been described in detail, it should be understood that the various
changes, substitutions, and alterations could be made hereto
without departing from the spirit and scope of the invention.
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